Question

S=1+2+3+.....+
S=1 +2 3+.....+
S=1+2+3.......+
S=2+4+6+.....+
S=2+4+6+.....+
S=2+4+6+......+




Unde e punctat trebuie să pui ce numar vrei tu.



Va rog repede dau coroana​

Answer 1

Răspuns:

S=1+2+3+...+20=[20(20+1)]/2=(21·20)/2=210

S=1+2+3+...+200=[200(200+1)]/2=(200·201)/2=20100

S=1+2+3+...+40=[(40(40+1)/2]=(40·41)/2=820

S=2+4+6+...+100=2(1+2+3..+50)=2·(50·52)/2=2·1275=2550

S=2+4+6+..+80=2(1+2+3+...+40)=2·(40·41)/2=80·41:2=1640

S=2+4+6+...+88=2(1+2+3+......+44)=2(44·45)/2=1980

Answer 2

S = 1 + 2 + 3 + ... + 34

S = 34 × 35 : 2

S = 1190 : 2

S = 595

S = 1 + 2 + 3 + ... + 76

S = 76 × 77 : 2

S = 5852 : 2

S = 2926

S = 1 + 2 + 3 + ... + 102

S = 102 × 103 : 2

S = 10506 : 2

S = 5253

S = 2 + 4 + 6 + ... + 40

S = 2 × ( 20 × 21 : 2 )

S = 2 × ( 420 : 2 )

S = 2 × 210

S = 420

S = 2 + 4 + 6 + ... + 88

S = 2 × ( 44 × 45 : 2 )

S = 2 × ( 1980 : 2 )

S = 2 × 990

S = 1980

S = 2 + 4 + 6 + ... + 124

S = 2 × ( 62 × 63 : 2 )

S = 2 × ( 3906 : 2 )

S = 2 × 1953

S = 3906